The present invention relates to the purification and fractionation of the influenza type virus and certain new or improved virus products obtained thereby useful for example, for immunological purposes.
The invention will in the following be described with particular reference to human influenza virus, particularly of the so-called "Hong Kong" type. It is pointed out however, that certain animal influenza virus types, e.g. horse influenza are very similar and thus the invention may be extended to application to such very similar virus materials as well. Where particular strains are referred to in this specification such is done purely by way of illustrative example. Other strains of influenza virus could be used with substantially similar results.
In our British No. Nol 1006258 (U.S. Pat. No. 3 415 804) we described and claimed the fractionation and purification of proteinaceous substances including viruses, using polyethylene glycol as an insolubilising agent capable of preferentially bringing about the insolubilisation (e.g. precipitation) of certain protein species under conditions where certain other proteinaceous species are substantially left in solution.
The process has since then been used successfully for the fractionation, purification and concentration of a variety of viruses.
In accordance with British patent No. 1 226 743 for example, there is described and claimed the purification of certain viruses, including influenza viruses under a set of conditions which are considered the optimum conditions by the particular patentees. One of the preferred parameters described in that application, is the use of 7.5% polyethylene glycol (p.e.g.) for optimum precipitation of influenza virus.
We have now discovered that further and/or alternative advantages are attainable using different parameters. We have further found ways of producing virus products different from those normally produced, including vaccines having improved properties.